#region Copyright & License

//
// Copyright 2001-2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#endregion

using System;
using log4net.Core;

namespace log4net.Util {
  /// <summary>
  /// Implements log4net's default error handling policy which consists 
  /// of emitting a message for the first error in an appender and 
  /// ignoring all subsequent errors.
  /// </summary>
  /// <remarks>
  /// <para>
  /// The error message is printed on the standard error output stream.
  /// </para>
  /// <para>
  /// This policy aims at protecting an otherwise working application
  /// from being flooded with error messages when logging fails.
  /// </para>
  /// </remarks>
  /// <author>Nicko Cadell</author>
  /// <author>Gert Driesen</author>
  public class OnlyOnceErrorHandler : IErrorHandler {
    #region Public Instance Constructors

    /// <summary>
    /// Default Constructor
    /// </summary>
    /// <remarks>
    /// <para>
    /// Initializes a new instance of the <see cref="OnlyOnceErrorHandler" /> class.
    /// </para>
    /// </remarks>
    public OnlyOnceErrorHandler() {
      m_prefix = "";
    }

    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="prefix">The prefix to use for each message.</param>
    /// <remarks>
    /// <para>
    /// Initializes a new instance of the <see cref="OnlyOnceErrorHandler" /> class
    /// with the specified prefix.
    /// </para>
    /// </remarks>
    public OnlyOnceErrorHandler(string prefix) {
      m_prefix = prefix;
    }

    #endregion Public Instance Constructors

    #region Implementation of IErrorHandler

    /// <summary>
    /// Log an Error
    /// </summary>
    /// <param name="message">The error message.</param>
    /// <param name="e">The exception.</param>
    /// <param name="errorCode">The internal error code.</param>
    /// <remarks>
    /// <para>
    /// Prints the message and the stack trace of the exception on the standard
    /// error output stream.
    /// </para>
    /// </remarks>
    public void Error(string message, Exception e, ErrorCode errorCode) {
      if (IsEnabled)
        LogLog.Error("[" + m_prefix + "] " + message, e);
    }

    /// <summary>
    /// Log an Error
    /// </summary>
    /// <param name="message">The error message.</param>
    /// <param name="e">The exception.</param>
    /// <remarks>
    /// <para>
    /// Prints the message and the stack trace of the exception on the standard
    /// error output stream.
    /// </para>
    /// </remarks>
    public void Error(string message, Exception e) {
      if (IsEnabled)
        LogLog.Error("[" + m_prefix + "] " + message, e);
    }

    /// <summary>
    /// Log an error
    /// </summary>
    /// <param name="message">The error message.</param>
    /// <remarks>
    /// <para>
    /// Print a the error message passed as parameter on the standard
    /// error output stream.
    /// </para>
    /// </remarks>
    public void Error(string message) {
      if (IsEnabled)
        LogLog.Error("[" + m_prefix + "] " + message);
    }

    #endregion Implementation of IErrorHandler

    /// <summary>
    /// Is error logging enabled
    /// </summary>
    /// <remarks>
    /// <para>
    /// Is error logging enabled. Logging is only enabled for the
    /// first error delivered to the <see cref="OnlyOnceErrorHandler"/>.
    /// </para>
    /// </remarks>
    bool IsEnabled {
      get {
        // Allow first error message to be logged
        if (m_firstTime) {
          m_firstTime = false;
          return true;
        }

        // Check if InternalDebugging is enabled
        if (LogLog.InternalDebugging && !LogLog.QuietMode)
          return true;
        return false;
      }
    }

    #region Private Instance Fields

    /// <summary>
    /// String to prefix each message with
    /// </summary>
    readonly string m_prefix;

    /// <summary>
    /// Flag to indicate if it is the first error
    /// </summary>
    bool m_firstTime = true;

    #endregion Private Instance Fields
  }
}